Dental prosthetic devices are becoming increasingly popular and are rivaling the use of removable dentures, partial dentures, or conventional bridges in replacing lost teeth.
A conventional dental implant device typically comprises two components, an implant fixture and an abutment. An implant fixture is imbedded into a patient's maxilla or mandible bone. An abutment is connected to the fixture and typically forms a support for a prosthesis, i.e., a crown, denture, partial bridge, or bridge. The implant fixture may be surgically implanted into the bone at various angles depending on several factors, such as the number of implants being placed into a corresponding section of edentulous (toothless) bone; the portion of the edentulous bone best suited to successfully support the implant; and the angle chosen by the dental professional in placing the implant. The abutment, however, must be aligned so that the dental prosthesis it will receive is generally parallel with other surrounding teeth, regardless of the angle at which the implant fixture is placed in the bone.
FIG. 1 shows a conventional dental implant system using the Branemark system where the implant fixture does not extend above the soft tissue. This system is described in Tissue Integrated Prosthesis, P. I. Branemark, G. A. Zarb, and T. Alberktsson, Chicago Quintessence Publishing Co. (1985). This is known as a submergible implant system. The mandible or maxilla 50, covered with soft tissue 52, has a number of implant fixtures 60 screwed into the bone 50 at various angles. Each implant has an abutment 65. The abutments are at generally parallel angles and, in this figure, support a support bar 67 retained on the abutments by screws 69.
It is preferable for the abutment to be selectably angled with respect to the implant fixture. For example, implant fixture 60a of FIG. 1 is implanted at an angle different than the angle necessary for proper alignment of the dental prosthesis. Thus, the abutment 65a must be able to be angled with respect to the implant fixture 60a so that a prosthetic tooth, or other prosthetic device, may be mounted at the proper angle with respect to the surrounding teeth or other prosthetic devices.
FIG. 2 is a cross-sectional view of a conventional dental implant in place in a patient's bone. A dental implant fixture 60 is screwed into place in a patient's mandible or maxilla 50. (In the case of an extraoral epithesis, the implant fixture is located in the appropriate bone.) This implant fixture 60 has an internal threaded opening which receives an abutment 65. The abutment has a head 67 shaped to receive a prosthetic tooth 70 (or other prosthetic device). Growing around the prosthetic tooth and implant above the mandible 50 is soft tissue 52. The soft tissue includes several layers including the epithelium layer 53 at the outer surface of the soft tissue; connective tissue 54; and the periosteum 56 located adjacent to the bone 50.
The dental implant procedure is done in several steps. This procedure is described in detail in Tissue Integrated Prosthesis, P. I. Branemark et al. First, a surgeon makes an incision in a patient's soft tissues 52, exposing the bone 50. A series of drilling procedures establishes a receptor site hole of a particular diameter in the bone. This is known as an osteotomy site. This osteotonomy site may be tapped to have threads, or the threads may be cut by a "self tapping" implant fixture. In either event, an implant fixture 60 is secured into the bone. A cover screw is screwed into the implant fixture internal thread to prevent soft tissue growth into the fixture internal thread. Several months pass to allow the bone to solidify around the implant fixture.
After six months, the soft tissue is again opened and the cover screw is removed. A healing abutment is screwed into the threaded opening in the implant fixture to perform two functions. First, the healing abutment closes the threaded opening. Second, the healing abutment allows the soft tissue to heal around the area of the incision, and can leave an opening or contour for the abutment and prosthetic tooth to be placed, or the tissue closes completely over the healing cap. The soft tissue heals to a desired contour. After several weeks or months, the healing abutment is removed. A post, standard abutment, or angulated abutment is positioned in the threaded opening. A dental prosthesis is positioned onto the post or abutment.
FIG. 3 shows a conventional healing abutment in place in a patient. A dental implant fixture 60 is implanted in a mandible 50. A dental implant healing abutment 72 is screwed into a threaded opening 74 in the fixture 60. The soft tissue 52 will heal around the superior portion of the fixture and the healing abutment. Because the implant fixture 60 may not have the same longitudinal axis as the standard abutment (and thus the prosthetic tooth), the healing abutment is designed to allow for a variety of rotational angles. As shown in FIG. 3, the healing abutment 72 has a conical shape extending upward from the superior portion of the implant fixture 60. This conical shape prevents the soft tissue 52 from healing around the healing abutment so that an unobstructed opening exists so that the abutment and dental prosthesis may be placed at a variety of angles with respect to the fixture 60. FIG. 3 shows (slightly exaggerated) extreme angles .alpha..sub.1 and .alpha..sub.2.
FIG. 4 illustrates one drawback of this conventional healing abutment. After the bone has solidified around the implant fixture 60 and the soft tissue has healed around the healing abutment 72, the healing abutment is removed and replaced with a post or abutment 65. The post or abutment is adjusted to the proper angle and a prosthetic tooth 70 is inserted onto the post or abutment 65. The healing abutment leaves a gap 74 around the base of the prosthetic tooth 70, which will never fill in. This gap 74 has several disadvantages. First, food particles and the like may become lodged in the gap and lead to infection and possibly gum disease. Secondly, the gap 74 is visible and is aesthetically unpleasant, particularly for front teeth which are easily observable, for example, when smiling.
Therefore, it is an object of the present invention to provide a healing abutment which allows soft tissue to heal at a proper angle without leaving an undesirable gap or undesirable contours.